The present invention relates generally to actuator control systems, and more specifically to systems for controlling one or more actuators in an effort to control a single operating condition in an internal combustion engine environment.
Actuator control systems are well-known and widely used in the automotive and diesel engine industries to control fuel systems, various valved mechanisms, engine and wheel brake systems, and the like. Many such actuator control systems utilize proportional-integral (PI) or proportional-integral-derivative (PID) controllers to achieve predictable and reliable actuator behavior.
While many different actuator control systems have been successfully implemented in a number of motor vehicle applications, some specific applications of known actuator control systems have a number of drawbacks associated therewith. For example, in known multiple-actuator control applications, open-loop control techniques have been used heretofore to control actuator behavior based on current engine operating conditions. However, such open-loop strategies typically require costly calibration and re-calibration of the engine controller. Moreover, such open-loop control strategies are necessarily overly conservative since they must take into account engine-to-engine variability, engine aging and variances in engine operation due to changes in altitude and other operational conditions.
As another example, single and multiple actuator control systems alike may have one or more dynamic gains associated therewith. Unfortunately, rapid changes in any of these dynamic gain values typically result in noticeable step-changes, or so-called xe2x80x9cbumpsxe2x80x9d, in actuator behavior. As yet another example, it is often desirable to limit the one or more actuator drive signals between upper and/or lower boundary values therefore. However, in known PI and PID controllers, the integral portion of the controller continues to integrate the input signal even though one or more of the actuator drive signals may be upper or lower bound saturated.
What is therefore needed is an accurate, closed-loop actuator control system applicable to single or multiple actuator systems that overcomes one or more of the foregoing drawbacks of prior art actuator control systems.
The foregoing shortcomings of the prior art are addressed by the present invention. In accordance with one aspect of the present invention, a closed-loop actuator control circuit comprises a first arithmetic circuit producing an error signal as a difference between an engine operating parameter signal and a reference parameter value, a controller responsive to said error signal to produce an actuator control signal, a first limiter responsive to said actuator control signal to produce a first actuator drive signal for driving a first actuator associated with a first engine control mechanism to minimize said error signal, and a second limiter responsive to a difference between said first actuator control signal and said first actuator drive signal to produce a second actuator drive signal, said second actuator drive signal driving a second actuator associated with a second engine control mechanism separate from said first engine control mechanism to minimize said error signal when said first actuator drive signal is limited by said first limiter to a maximum first actuator drive signal limit.
In accordance with another aspect of the present invention, a closed-loop actuator control circuit comprises a rate limiter limiting a proportional gain value to a rate-limited gain value based on a maximum gain change rate value, a first arithmetic circuit producing a proportional signal as a product of an engine operating parameter error signal and said rate-limited gain value, a controller circuit producing an actuator control signal based at least in part on said proportional signal, and a limiter circuit limiting said actuator control signal to between upper and lower limit values and producing an actuator drive signal corresponding thereto for driving an actuator associated with an engine control mechanism to minimize said error signal.
In accordance with a further aspect of the present invention, a closed-loop actuator control circuit comprises an integral circuit integrating an engine operating parameter error signal to produce an integral signal, a first arithmetic circuit producing an actuator control signal based at least in part on said integral signal, a limiter circuit limiting said actuator control signal to between upper and lower limit values and producing an actuator drive signal corresponding thereto for driving an actuator associated with an engine control mechanism to minimize said error signal, and an anti-windup circuit having a first input receiving said upper limit value, a second input receiving said actuator control signal delayed in time and a third input receiving said error signal, said anti-windup circuit disabling integration of said error signal by said integral circuit if said actuator control signal delayed in time is greater than said upper limit value and said error signal is greater than a predefined error value.
One object of the present invention is to provide a closed-loop actuator control circuit operable to control multiple actuators with a single PI controller in order to minimize an error between an engine operating parameter and a reference parameter.
Another object of the present invention is to provide a PI actuator control circuit having a proportional gain circuit configured to limit the rate of change of the proportional gain term to thereby ensure satisfactory signal tracking performance for sudden variations in the proportional gain term and provide for smooth (i.e., xe2x80x9cbumplessxe2x80x9d) gain scheduling.
Yet another object of the present invention is to provide a PI actuator control circuit having an anti-windup circuit configured to provide for dynamic saturation of the PI integrator by disabling positive integration if the actuator drive signal output is upper-limited bounded and disabling negative integration if the actuator drive signal is lower-limit bounded.
These and other objects of the present invention will become more apparent from the following description of the preferred embodiment.